The present invention relates to a packaging system for filling bulk material into open containers, a compacting device for compacting bulk material in an open container and a method for filling and/or compacting bulk material into or in an open container. Although the invention will now be described with reference to filling bulk material into open bags and to compacting bulk material in open bags, the invention is not limited to filling bulk material into open bags and to compacting bulk material in open bags but it may likewise be employed for filling bulk material into other open containers or receptacles such as cartons, buckets, or other open containers and to compact them therein.
The prior art has disclosed a great variety of apparatus and methods for filling bulk material into open containers such as open-mouth bags and compacting during or after the filling process so as to reduce the quantity of bag material required and to allow better and easier stackability of filled and closed bags.
When filling bulk material into open bags a fluid such as air may be added to increase flowability of the bulk material. In the case of very lightweight materials a considerable portion of air tends to be present in the bulk material before filling starts. In order to reduce the required container size and also the transport costs, the open containers are actively or passively deaerated during or after filling to reduce the air content in the bulk material.
For better compacting the filled bulk material, bottom vibrators have been disclosed which act upon the container bottom and considerably contribute to deaerating bagged bulk material by way of the introduced vibrations. For some bulk materials such compacting is not sufficient or compacting takes too long so that the filling rate efficiency decreases.
DE 10 2005 037 916 A1 has disclosed a machine for forming, filling and closing bags which manufactures bags from a plastic tube and in a filling station a downspout of a batching element is inserted into the open-top end of the bag. The downspout is provided with a screw conveyor for transporting the filled material to thus fill the bag. The downspout is surrounded by a closing tube. During the dosing process a separate conveying system lowers the bag during filling in such a way that the product discharge opening will at all times be positioned beneath the filled level. If required, suction combined with the dosing process is possible through the filter integrated in the closing tube, wherein air suction results in compacted bulk material to a certain degree. This effect of product compacting may be enhanced further by additionally employing vibration generators or rappers. Such rapping on the closing tube from outside will be done on top immediately beneath the hopper. The vibrations are transmitted through the closing tube and the downspout into the filling material. In the alternative a vibrator may be disposed at the bag bottom support unit and act onto the bag bottom from beneath. The known machine shows the drawback that conveying the product through a conveyor screw in the downspout requires a relatively large diameter of the batching element and can only provide rather low filling rates. Lowering the bag during the filling process also takes time and furthermore involves considerable complexity of apparatus. There is also the considerable disadvantage that the metering tube requires a large batching element diameter so as to only allow filling bags showing a large enough diameter at the top end. Moreover relatively little energy and just a small vibration amplitude can be introduced into the filled product so that efficiency is limited.
Therefore, using vacuum lances has been disclosed which enter into an open bag from above during the filling process, inducing air through an applied vacuum by way of the outer lance surface and carrying off the air in the interior. These vacuum lances increase the filling rate in particular in the case of lightweight bulk materials, even though bulk material tends to build up caking on the outer vacuum lance surface during the filling process so as to considerably reduce the efficiency of the vacuum lance since outer regions are no longer reached. Moreover the filter may become clogged over time.
An efficient method has been found to be the use of a poker vibrator which is also inserted into the open bag from above through the filling spout and which shows a rotatably supported imbalance in the interior of the poker vibrator serving as a vibration exciter and causing vibrating movement of the poker vibrator during rotation, so that the bulk material surrounding the poker vibrator is deaerated. In the case of particularly lightweight bulk materials it may be less than efficient to use a poker vibrator, perhaps because the poker vibrator tends to rather be stirring the bulk material around if the material is that lightweight, instead of achieving efficient deaeration.
DE 10 2011 119 451 A1 has disclosed a packaging machine for filling bags which allows high filling rates combined with high weight accuracy. The known packaging machine provides for using filling turbines for conveying the filling product. Two separate compacting devices are assigned to each of the filling spouts. A compacting device is configured as a bottom vibrator and disposed beneath the bag bottom. During the filling process a vacuum lance serving as another compacting device may enter the bag interior from above through the filling spout, compacting the filled product. It is noted that it is possible to optionally or product-related or successively insert a poker vibrator serving as a compacting device and a vacuum lance serving as a compacting device into the filling spout from above. Although the known packaging machine operates satisfactorily, it shows high complexity due to the high number of different compacting devices and pertaining adjustment devices. For bagging particularly lightweight materials, devices and methods have been disclosed where external pressure is applied on the bags while bulk material is filled into flexible bags to generate high internal pressure so as to achieve a considerably improved deaeration performance due to the high pressure difference to the ambience. This method shows the drawback, however, that the filling mouth requires pressure-tight sealing and that process control requires either the use of a pressure sensor or meticulous execution to prevent the flexible bags from bursting which would contaminate the ambience.
It is therefore the object of the present invention to provide an apparatus and a method and a packaging system which allow efficient filling and deaerating also of lightweight bulk materials while involving relatively little complexity.